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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

WOOL FAT STEARINE                           453

The saponification number is equal or almost equal to the acid number with
.pomfied stearine and somewhat greater with distillation stearine

The iodine number is barely a few units in good saponification stearines
but may reach 15-30 m distillation stearines, owing to the presence of iso-oleic
acid.

sa1

WOOL   FAT   STEARINE

This is the solid part of distiUed wool fat and consists of fatty acids and
unsaponifiable substances (hydrocarbons, cholesterol).

According to the consistency, it is distinguished as Soft stearine, melting
below 45°, and Hard stearine or Wool fat wa%, melting above 45°.

In general, these products have a waxy appearance, a yellow or brownish
colour and a pronounced odour of wool fat, and they are soluble in hot
alcohol and in ether, benzene or chloroform. When treated with cone,
sulphuric acid, the chloroform solution turns red and afterwards violet
with a green fluorescence (cholesterol).

Analysis of wool fat stearine includes determinations of the melting
point, acid number and content of unsaponifiable substances, as well as
tests for added hydrocarbons (vaseline, paraffin wax) or resin.

1.  Vaseline or Paraffin Wax.—The unsaponifiable substances from
50 grams of the stearine are boiled for 2 hours in a reflux apparatus with
double their weight of acetic anhydride.   The product is then washed
repeatedly with boiling water until the reaction is neutral and in one part
the acetyl number is determined (see p. 378).   Another part (about 5
grams) is boiled with 50 c.c. of 90% alcohol, the liquid being filtered off
and the residue boiled with 40 c.c. and then with 30 c.c. of 90% alcohol.
Of the part insoluble in alcohol, which consists of hydrocarbons alone, the
specific gravity, rotatory power (in benzene solution at about 20°) and
iodine number are determined.

2.  Resin.-.....-This is tested for as in wool fat oleine (see p. 451).

*
* *

According to M'arcusson and Skopnik * and to Coen,2 wool fat stearines
may melt between 40° and 65° ; they contain 56-90% of free acids (calculated as
stearic acid) and 9-42% of unsaponifiable substances, which are brown, fluores-
cent, pasty or semi-liquid masses with a faint aromatic odour and have the
acetyl number about 25-37, the [a]D + 12° to + 30° and the iodine number
4.7-74.

The portion of the unsaponifiable matter which does not combine with
acetic anhydride (hydrocarbons free from higher alcohols) has 0=0-907-
°'936> MB = + -'2° to -f- 21°, and iodine number =26-54.

" 'Addition of extraneous hydrocarbons may be suspected when the acetyl
number of the unsaponifiable substances is less than 25 and the portion of them
not combinable with acetic anhydride has a specific gravity less than 0-9, [a]D
less than -f 12° and an iodine number less than 26.

1  Zeilschr. angew, Chem., 1912, p. 2577.

2  Annali del Lab. cMm. centrale delle Gabelle, Vol. VI, p. 567- 10°, fat.